Point-Data FB and Measurement Function-Blocks

You might also call the Point-Data FB a 'Point Sensor', and the Measurement FB a 'Dimension Sensor'.

It is important to note, that the output from FBs have three 'data-channels', which are the three motion-derivatives.

These FBs can be used in two different ways:

Make a plot of a kinematic parameter.

Connect a wire from the output-connectors of a Point-Data or Measurement FB to the input-connector of a Graph FB.

Use the motion-values from these FBs as an independent-variable.

Connect a wire from the output-connector of a Point-Data or Measurement FB to the input-connector of a different FB to become the independent-variable of a different kinematic-chain.

This is called a Motion-Dependency. The '2nd' kinematic-chain is motion-dependent on the '1st' kinematic-chain.

About the 'Independent-Variable'

When we design a Motion (in MotionDesigner) and link it to a Motion FB, the independent variable (input) is the motion-value at the input-connector to the Motion FB. Usually the motion-values at the input to a Motion FB continually increase, at a constant rate; for example, from a Linear-Motion FB. This is the most typical way we connect FBs.

However, it is also possible that the motion-values at the input-connector to a Motion FB do not continually increase.

The input to the motion may actually be any 'function'. Thus, the motion-values may be from a Measurement FB, a Point-FB, or even another Motion FB.

tog_minus        Point Data (or Measurement Data FB): Make a plot of the Motion Values with a Graph FB

We will use a Graph FB to make a plot of the motion-values.

Icon-FB-PointData

Use a Point-Data FB to make a plot of the kinematic data of a Point element.

STEP 1: Assemble a kinematically-defined chain - for example a Crank!
STEP 2: Add a Point-Data FB to the graphic-area

To link the Point-Data FB with a Point in the graphic-area:

STEP 3: Double-click the Point-Data FB.
STEP 4: Click a Point that moves in the kinematically-defined chain.
STEP 5: Click OK in the Point-Data dialog-box

To make a plot of the Kinematic Data for the Point:

STEP 6: Add a Graph FB to the graphic-area
STEP 7: Connect a Point-Data FB to one of the four input-connector on the Graph FB
STEP 8: Connect a Linear-Motion FB to the Graph FB X-axis (the bottom connector) (not strictly necessary - Release 7+)
STEP 9: Open the Graph FB. Double-click the Graph FB in the graphic-area.

After you follow these steps, you can see all of the elements in the image below.

The Base-Value of the Motion-Dimension FB and the Phase of the Linear-Motion FB are 0º. The motion-values connected to the X-axis of the Graph are equal to the MMA.

QST6-2-5

Rotate a Crank at constant angular velocity. Use a Linear-Motion FB and a Motion-Dimension FB.

Make the Crank 50mm long.

The end of the Part will have a horizontal and vertical range of +50mm to -50mm about its centre-point, with a sinusoidal function in the X and Y directions. The sinusoid for Y lags the X value by 90º.

 

The Pin-Joint for the Part is 20mm above the 0,0 of the Base-Part and Mechanism-Editor.

Link the Point at the end of the Rotating-Part with a Point-Data FB.

Connect the X and Y outputs of the Point-Data FB to the Graph FB. Open the Graph FB.

 

The MMA angle is 120º, as shown by the red pointer below the MMA slider, and the vertical red line in the Graph.

The DROs (Digital Readouts), below the Graph, give the Y1 (=X coordinates of the Point), and Y2 (=Y coordinates of the Point).

 

You can see:

the Blue graph has a range of -50 to +50mm
the Green graph has a range -30 to 70mm.

 

Top-Tip

To show the position, velocity and acceleration of a Point in the same graph.

1.Drag a wire from the same output-connector of the Point-Data FB three times to three different input-connectors on a Graph FB,
2.Use the Y-axis display options in the Graph dialog-box to display each motion derivative.

tog_minusMeasurement FB: Gives the motion values as the Independent Variable to a different Kinematic Chain

Icon-FB-Measurement

Below, there are two kinematically-defined chains:

The Kinematic-chain #1 uses a Linear-Motion FB as the independent variable. The independent-variable is the 'X-axis' input to the Motion-Dimension FB#1.

The output to the Rocker from the Motion-Dimension FB#1 is simple: it is its X-axis input PLUS its initial offset value, which we call its Base-Value parameter.

We take a measurement between a Point and a Line in the 'First' kinematically-defined chain, with a Measurement FB

The Kinematic-chain #2 takes the output from the Measurement FB as the X-axis input [independent variable] to the Motion-Dimension FB#2.

Thus, the output from the Motion-Dimension FB#2 is simple: it is the input from the Measurement FB PLUS the Base-Value parameter.

Kinematic-Chain #2 has 'Motion-Dependency' on Kinematic-Chain #1.

STEP 1: Add a Measurement FB to 'capture' motion-values 'somewhere' in the 'First' kinematic-chain
STEP 2: Connect the Measurement FB to the Motion-Dimension FB of the second kinematically-defined chain.

QST6-5-1A

Kinematic-Chain 1 – a Crank

Rotate a Crank at constant angular velocity. Connect a Linear-Motion FB to the input of a Motion-Dimension FB.

Make the Crank 50mm long.

 

Kinematic-Chain 2

Connect the Measurement FB to the input of a different Motion-Dimension FB.

 

The Measurement FB shows, in this case, the distance between two Points. The distance between the two Points continually changes as the 'machine' cycles.

 

The Base-Value of #2 Motion-Dimension' is 0º.

Hence the Motion-Part that the Motion Dimension specifies the motion for, will be the same as the output from the Measurement FB, and continually change as the model cycles.

 

The distance between two Points is 45.14mm, as shown in:

the graphic-area
the Graph:

Therefore, the Angle of the Rocker is 45.14 degrees.

tog_minusMeasurement FB: connected to a Motion-Part via a Gearing FB

Icon-FB-Measurement

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Icon-FB-Gearing

There are two kinematically-defined chains:

The 'First' kinematic-chain uses a Linear-Motion FB as the independent variable to move it.
The 'Second' kinematic-chain uses the output a motion-values derived from the Measurement and Gearing FBs as the independent variable.
STEP 1: Add a Crank
STEP 2: Add a Measurement FB to 'capture' the motion-values somewhere in the ''First' kinematic-chain.
STEP 3: Add a Gearing FB to the graphic-area.
STEP 4: Double-click the Gearing FB and change the Gearing Ratio to 0.5
STEP 5: Connect the Measurement FB to the Gearing FB
STEP 6: Connect the Gearing FB to the Slider Motion-Dimension FB of the 'Second kinematic-chain'

A screen capture below shows a graph that illustrates the connection of a Measurement FB to a Motion-Dimension FB drives the Slider Part of a different kinematic-chain.

QST6-5-4

Kinematic-Chain 1 – a Crank

Connect a Linear-Motion FB to a Motion-Dimension FB to rotate a Part at constant angular Velocity - a crank.

The angle of the Motion-Dimension is 120°. This is the same as the MMA.

The Base-Value of the Rocker Motion-Dimension FB is 0°

 

A Measurement FB gives the distance between two Points.

The distance between the two Points continually changes as the 'machine' cycles.  The measurement is 127.99mm, say 128mm

 

We connect the output from the Measurement FB to a Gearing FB. Its ratio is 0.5. Hence its output is 64.00mm

 

Kinematic-Chain 2

Connect the Gearing FB to the Motion-Dimension FB to drive a Slider.

The Base-Value of Slider Motion-Dimension has is 0mm.

Hence, the Motion-Dimension is the same as the output from the Gearing FB as the 'machine' cycles.

tog_minusMeasurement FB: connected to a Motion FB connected to a Motion-Dimension FB

Icon-FB-Measurement

+

Icon-FB-Motion

There are two kinematically-defined chains.

The 'First' uses a Linear-Motion FB to move a Rocker. It is a Crank.
The 'Second' uses the output from a Motion FB as its independent variable, which itself uses the output from a Measurement FB as its independent variable.
STEP 1: Add a Crank as the first kinematic-chain
STEP 2: Add a Measurement FB to measure the motion-values somewhere in the 'First' kinematic-chain
STEP 3: Add a Motion FB to the graphic-area. Edit it to link to it a Motion in MotionDesigner.
STEP 4: Edit the Motion in MotionDesigner.
STEP 5: Connect the output-connector of the Measurement FB to the input-connector of the Motion FB
STEP 6: Connect the Motion FB to the Motion-Dimension FB of the 'Second' kinematic-chain

OpenMotionFBPopupQST6-5-5

'FIRST kinematic-chain' – Crank

Connect a 'Linear-Motion FB' to a Motion-Dimension FB to model a crank.

The angle of the Motion-Dimension is 120°. This is the same as the MMA.

The Base-Value of the Rocker Motion-Dimension FB is 0°

 

A Measurement FB show the distance between two Points. The distance between the two Points continually changes as the 'machine' cycles.  The measurement is 127.99mm – say it is 128mm

 

We connect the Measurement FB to a Motion FB. The Measurement FB 'acts' as the independent variable (X-axis) of the Motion linked with the Motion FB.

 

If you click here, or where indicated on the image 'hotspot' to the left, you will see the output from the motion is approximately 55 when the independent variable (X-axis value) is 128

 

SECOND kinematic-chain

Connect the Motion FB to the Motion-Dimension FB. The Base-Value of Motion-Dimension is 0mm.

Therefore, the Motion-Dimension will continually agree with the output from the Motion FB as the 'machine' cycles.

Connect the output from the Measurement FB to the input of the Motion FB.

Each value at the input to the Motion FB acts as the X-axis value for the motion graph, in MotionDesigner, to give a Y-axis value at the output-connector of the Motion FB.

 

The output from the Measurement FB:

can increase and decrease
does not change steadily
may be greater than 360

Irrespective of the motion-value at the output from the Measurement FB, the Motion FB outputs a motion value that corresponds to the Y-axis value given the X-axis value.

tog_minusDevelop a Stationary Cam

Icon-FB-PointData

Icon-FB-Measurement

An important application the Point-Data and Measurement Function-Blocks is to develop 'Stationary Cams'.

See Tutorial 6D Design 2.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd